Photogelatin printing



Jan. 16, 1934.

J. A. FLEISCHMANN El' AL PHOTOGELATIN PRINTING Filed Sept. 4, -1930 91H. arl/vi roar/Nq .en/(Eq fra/N50 Msi/r1. P4 #rf lil Patented Jan. 16, 1934 UNITED STATES PHoToGELATIN PRINTING Jacob A. Fleischmann, Walton W. Sullivan, and Frank 0. Sullivan, Cleveland, Ohio, assignors to Gardner Abbott, Cleveland, Ohio Application september 4, 1930. serial No. 479,724

8 Claims.

This invention relates to methods and appliances for the production of single or multiple photo-gelatin plates for monochrome and color register printing by projection, and aims generally to improve such processes and plates and produce ne color work of any size at low cost by either flat bed or rotary, direct or oiset, presses.

Although our invention is particularly advantageous as applied to large size plates for printing pictorial work in any number of colors, it is applicable to any photo-gelatin or similar type of plates, and to all kinds of printing, including half tone and full tone photo-reproductions of paintings, photographs, line drawings, crayon drawings, letter press, and composite work, heretofore not produced by photo-projection methods.

The invention aims to secure the full detail and truthful reproduction of the colors and tones of the original copy when applied to one color or to multi-color printing, and to produce a softer effect and to improve the brilliancy and tone values of the printing copies as compared with those made by existing commercial processes and plates.

The invention further aims to shorten the time and reduce the cost heretofore required to make a set of color printing plates of the photo-gelatin type, and to produce a durable printing surface that will make a great number of impressions before losing its sharp detail.

An important advantage of our invention is its adaptability to the direct projection of normal size continuous tone image, as for example an eight by ten inch photographic negative, or any filtered or screened image or set of images, to any size desired without the intervention of a screen or other means for breaking up the image into printing dots, this being the rst'time in the graphic arts that such a result has been accomplished so far as We are aware.

Other aims and advantages of the invention appear or will occur to those skilled in the art in connection with the following-description of -a preferred embodiment, illustrated diagrammatically in the accompanying drawing, wherein Fig. 1 is a side view of a suitable projection device;

Fig. 2 is a cross-section of a plate before exposure;

Fig. 3 is a similar view of the plate after eX- posure; and

Fig. 4 is a cross-section of the plate after washing to swell the gelatin where not exposed and leave the image slightly sunken beneath the generalv plane of the unexposed portions of the surface.

According to the illustrated form of the invention a suitable sheet 11, as a metal plate of zinc or aluminum or other soft ductilemetal or alloy suitable for a printing plate, is lightly grained on its printing side and dried in an oven for the purpose of holding the light sensitive material; it is coated in a whirler or other coating device with two coatings, 12, 13, of gelatin, the second of which contains a sensitizer of potassium bicromate or other light sensitive material, and each of which is dried by whirling or otherwise. Preferably the coated plate is dried in an oven for three hours at 90 F. or more to harden the coatings, the temperature and time being correlated to effect the desired texture of grain in the coating. (See Fig. 2.)

The coated plate is then ready to be exposed to actinic light rays 14 passed through a transparent image l5 as shown in Fig. 1 and carrying the image directly to the printing surface of the printing press plate. A suitable apparatus comprises a source of light 16, a condenser 17, negative holder 18, lens 19, and plate holder 20, which -may be arranged in a darkened room or room having no direct daylight. Preferably the lenses and negative holder are mounted in a suitable camera 21 having means for adjusting them with respect to each other and the plate holder. Other types of apparatus may be employed, as the invention contemplates projecting or photographing the image onto the coated plate by actinic light rays, in any suitable manner.

The source of the light rays is preferably a carbon arc lamp so constructed that the positive carbon is disposed in vaxial alignment with the direction of the projected rays, and is caused to revolve constantly so as to maintain a crater at its point which holds a small volume of incandescent gas or vaporized metals produced by the arc, the particular vapor depending on the kind of carbon electrode used.

The coated plate will be affected where struck by suitable light rays as is indicated in Fig. 3,l where the non-light-struck portions 22 and the light-struck portions 23 are clearly indicated. The intensity and character of the light rays have an important bearing on the speed of the exposure and the character of the photo-gelatin plate produced, and we have discovered that a rotating carbon arc lamp taking about one hundred and twenty-rive amperes at one hundred and ten volts produces satisfactory results. Whether this is due to peculiar properties of the projecting ray or to increased intensity of the ray, is not known to us. It is suggested, however, that the improvement in quality and longevity of the light affected portions may be due to the different spectral energy distribution in the rays from such high powdered light source and to the heating of the light struck portions of the plate. The rays reaching the sensitized material which come from a projection apparatus employing a high powdered carbon arc of the type described may Wellcontain a greater percentage Cil than, sun light or rays from a low powered source of rays which will assist or cause the completion of the chemical action between the gelatin and the bichromate and produce a further toughening of the light struck portions of the photo-gelatin layer so as to increase the longevity of the plate for printing purposes. The greater temperature of the light exposed portions duringl such exposure may also contribute to the increase in toughness and longevity.

As soon as the plate has been sufiiciently exposed to the actinic rays of light, which may be from ve to ten minutes, more or less, when using potassium bichromate as a sensitizer, depending upon the density of the negative, the strength of color desired in the reproduction, and the size of the projected image, it is developed under running water for fifteen minutes to wash out the chemicals in the unexposed parts of the coating, drained off and allowed to dry. When taken to. the pressroom, where it undergoes the usual treatment in preparation for printing, it is preferably placed in a bath of glycerine and water of equal parts and soaked for fifteen minutes immediately before use.

'I'he effect of the actinic light upon the portions of the coating constituting the image is to transx and harden the gelatin where the light strikes, making it impermeable to water and giving it a durable character, which prevents the water development from softening or penetrating the image, and greatly prolongs the life of the plate in the press. This transflxatlon of the gelatin to form the image characterizes the plate.

The effect of the water development of the plate is to cause the unexposed portions of the coating to swell, as shown in Fig. 4, leaving the image slightly in intaglio, and the raised portions being ink-repellent, the plate may be printed on any direct inking plate press with an occasional spraying with glycerine and water to maintain its surface in good printing condition. Presses having both nap and composition rollers traversing tll: plate in the order named give the best res ts.

Our process of making photo-gelatin printing plates is very rapid, and much less expensive than by the usual method of procedure which requires a negative of the size of the reproduction desired. But a few hours are required for the completion of a set of plates for printing in four or more colors, the usual process color separation negatives being suitable and no retouching of the plates being necessary.

Photo-gelatin printing plates made according to our invention are entirely suitable for multi-color work, and faithfully reproduce, without screen or `other interference of any character, all of the ne lines, tintsand tone effects of the original copy.

The invention is not restricted to the exact ingredents and methods described, but what it is desired to secure by Letters Patent is as follows:

1. The process of making photo-gelatin. printing plates that comprises graining a suitable plate to take a coating, coating the grained surface with a gelatin and drying the same, applying a second coating of gelatin which contains a sensitizer of the potassium bichromate type, baking the coated plate at approximately 90 F. f or a period of about 3 hours, exposing the baked plate without the interposition of a screen to high intensity actinic rays from a carbon-arc projected directly through a transparent image for a period of minutes, and developing the light struck plate in flowing water.

2. The process as set forth in claim 1 in which lradiant actinic rays of the kind emitted by a rotating carbon arc drawing about-one hundred and twenty-five amperes at a potential of about one hundred and ten volts are used to effect the image projection.

3. In the process of making a collotype photogelatin printing plate of the bichromate-sensitized type, the step comprising exposing the sensitized plate to high intensity rays projected through a transparent image, said rays having the intensity and character of those emitted by a rotating carbon-arc drawing about 125 amperes at about 110 volts and the exposure being continued for about five to ten minutes, more or less, thereby producing printing image portions characterized by marked toughness and high durability.

4. In the process of making a collotype photogelatin printing plate of the bichromate-sensitized type, the step comprising exposing the sensitized plate to the rays projected through a transparent image from a rotating carbon-arc drawing about 125 amperes at about`110 volts for ve or more minutes.

5. In the process of making a collotype photogelatin printing plate of the bichromate sensitized type, the step comprising exposing the sensitized plate to the rays projected through a transparent image from a carbon-arc having a continuously rotating positive electrode directed normally to the plane of the plate and drawing about 125 amperes at 110 volts for several minutes.

6. The process of making a photo-gelatin printing plate having an intaglio printing image, comprising coating a suitable plate with bichromate-sensitized gelatin, baking the coated plate, exposing the baked plate Without the interposition of a screen to high intensity rays projected through a transparent image, said rays having the intensity and character of those emitted by a rotating carbon-arc drawing about 125 amperes at about 110 volts, and developing the light struck plate in flowing water.

'7. A photo-gelatin printing plate of the bichromate type having continuous intaglio printing image portions characterized by the marked toughness and high durability resulting from exposure continued for several minutes of the sensitized gelatin to rays having the intensity and character of those from a rotating carbin-arc drawing about 125 amperes at about 110 Volts.

8. A photo-gelatin printing plate of the bichromate type having continuous intaglio printing image portions characterized by the marked toughness and high durability resulting from exposure continued for several minutes to rays from a carbon-arc drawing about 125 amperes at about 110 volts and having a continuously rotating positive electrode axially disposed to the direction of the rays.

JACOB A. FLEISCHMANN.

WALTON W. SULLIVAN.

FRANK O. SULLIVAN. 

